GB791751A - Improvements in or relating to blades for axial flow gas turbine engines, and to methods of making such blades - Google Patents

Abstract

791,751. Gas turbine blades. BRISTOL AERO-ENGINES, Ltd. Dec. 31, 1954 [Jan. 6, 1954; April 5, 1954], Nos. 422/54 and 9961/54. Class 110 (3). [Also in Group XXII] A blade for an axial flow gas turbine comprises an aerofoil portion and a root portion and two cooling fluid passage systems extend through the aerofoil portion from near the root end thereof to near the tip. The two passage systems are confined to the leading and trailing portions of the chord-wise width, the intermediate portion of the aerofoil portion being solid and extending over about one-third of the chordwise width of the blade at least at the root end. Separate inlet passages extend through the root portion to the leading edge and trailing edge passages and outlets extend from the leading edge and trailing edge passages to the surface of the blade at or near the tip. The passages of the passage systems are defined by heat transfer elements in good heat conducting relation with the outer surface of the blade. The aerofoil portion 5 of the blade shown in Figs. 2 and 3 is formed with groups of narrow grooves 24 spaced by fins 33. The grooves in the leading edge group 11 open at their ends in two chambers 27 29 and the trailing edge group 12 open into chambers 28, 30. The grooves are formed from one face of the blade which is covered by a plate 31 brazed in position to constitute the concave surface of the blade. The leading edge inlet chamber 27 connects by a circular cooling fluid inlet passage 13 to the front surface of the root portion, while the outlet chamber 29 which is of approximately quadrilateral shape, is connected to a fluid outlet passage 19 which is also of quadrilateral shape, in the shroud portion 21. The trailing edge inlet'chamber 28 is connected by a cooling fluid inlet 14 of triangular section to a side face of the stem portion of the blade root, while the trailing edge outlet chamber 30 opens out at 22 on to the convex blade surface. The grooves 24 may be formed by spark erosion or by ultrasonic machining. Instead of a plate 31, the open grooves and header chambers may be closed by first filling them with wax or a low melting-point metal, then plating electrolytically or by spraying with a sufficient thickness of a high melting point metal, the low melting point filler being finally melted out. In a second embodiment, Figs. 6 and 7, the leading and trailing edge passage systems 11, 12 are each formed with a plurality of spaced pinlike members 100 disposed transversely to the length of the blade. The header chambers 27, 28, 29, 30 and cooling fluid inlet and outlet passages are formed as in the first embodiment. The passages and pin-like projections are formed by means of a spark erosion or ultrasonic machining operation using electrodes formed with openings corresponding to the pin-like projections. The passages are closed by a plate 31 similar to that in the first embodiment. In Figs. 11, 12 and 14, the leading and trailing edge passage systems are formed by series of narrow grooves 24 as in the first embodiment but the grooves are continued right into the root portion and emerge at 76 into a face of the stem portion 57 of the' blade root. Cooling fluid tunnels are formed between adjacent blade root stem portions and the outer periphery of the rotor, the tunnels being closed at one end by tooth-like projections 66 at one side of the rotor periphery. Cooling fluid entering the tunnels passes into the cooling fluid passage systems through the grooves 76. The grooves 24 are covered by a plate 78 which is bent round the blade stem portion. The fins 33 between the grooves 24 are tapered at the tip portion to provide header chambers of triangular section. Specifications 763,679 and 791,752 are referred to.